JP5623037B2 - Spraying material and spraying method using the same - Google Patents

Description

  The present invention mainly relates to a spraying material used in the civil engineering and construction industry and a spraying method using the same.

In order to prevent collapse of exposed ground such as tunnel excavation, a spraying method of quick setting concrete in which a quick setting agent is mixed with concrete is performed (see Patent Document 1). This method usually involves preparing sprayed concrete at a cement, aggregate and water metering and mixing plant installed at the excavation site, transporting it with an agitator car, pumping it with a concrete pump, and using a confluence pipe installed in the middle. This is a method of mixing with a rapid setting agent fed from the other side and spraying it to the ground surface as a quick setting sprayed concrete until a predetermined thickness is reached.
Accelerating agents include calcium aluminate, a mixture of alkali metal aluminate and alkali metal carbonate, etc., and a mixture of calcium aluminate, alkali metal aluminate, alkali metal carbonate, and calcium aluminate. And 3CaO · SiO ₂ are known (see Patent Documents 2 to 5).

  The quick setting agent is an admixture necessary for shotcrete to suppress the loosening of natural ground at an early stage, but the shrinkage tends to be larger than the concrete without the quick setting agent. Generally, the larger the value, the larger the difference.

Japanese Patent Publication No. 60-4149 Japanese Patent Laid-Open No. 64-051351 Japanese Examined Patent Publication No. 56-27457 JP-A-61-026538 JP 63-2105050 A

  The present invention relates to a spray material capable of suppressing cracking by reducing the amount of shrinkage due to temperature stress and drying by applying calcium carbonate of a specific particle size and a rapid setting agent to cement concrete, and a spraying method using the same I will provide a.

That is, the present invention comprises (1) calcium carbonate having a Blaine specific surface area of 500 to 1800 cm ² / g, a quick setting agent , cement, and an aggregate, wherein the quick setting agent contains aluminum sulfate, It is a spraying material which is 2-50 mass parts of said calcium carbonate with respect to a mass part, It is a spraying construction method using the spraying material of (2 ) ( 1 ) .

  By using the spray material of the present invention, it becomes possible to suppress cracking by reducing the amount of shrinkage due to temperature stress and drying, and it is possible to obtain spray concrete excellent in durability.

  The parts and% used in the present invention are based on mass unless otherwise specified.

Cement used in the present invention is usually various Portland cements such as early strength, very early strength, low heat, and moderate heat, and various mixed cements obtained by mixing these Portland cements with blast furnace slag, fly ash, or silica, Environmentally friendly cement (eco-cement manufactured using filler cement mixed with limestone powder exceeding 2,000 cm ² / g in Blaine specific surface area, ground granulated blast furnace slag, etc., and municipal waste incineration ash and sewage sludge incineration ash as raw materials Portland cement such as), and one or more of these can be used.

The calcium carbonate having a brain specific surface area of 500 to 2000 cm ² / g used in the present invention is not particularly limited, and examples thereof include pulverized and adjusted limestone as a raw material.
The purity of calcium carbonate in limestone is not particularly limited, but is preferably 95% or more.

The amount of calcium carbonate having a Blaine specific surface area of 500 to 2000 cm ² / g is not particularly limited as long as it does not affect the workability and the physical properties after curing, but is 2 to 100 parts of cement. 50 parts are preferable, and 5 to 30 parts are more preferable. If it is less than 2 parts, the effect of improving crack resistance may not be exhibited, and if it exceeds 50 parts, strength development may be affected.

Calcium carbonate having a brain specific surface area of 500 to 2000 cm ² / g may be added to one or both of the concrete side and the quick setting agent side when spraying concrete.

The quick setting agent used in the present invention contains any component selected from calcium aluminate, alkali metal aluminate, alkali metal silicate, and aluminum sulfate, and is used commercially. It is possible and the thing containing the said component is preferable.
For example, those containing calcium aluminate include calcium aluminate powder quick setting agent, calcium sulfoaluminate powder quick setting agent, and water and liquid quick setting agent mixed with them to make a slurry. Is mentioned. Examples of those containing an alkali metal aluminate include inorganic salt-based powder quick-setting agents and inorganic salt-based liquid quick-setting agents. As what contains an alkali metal silicate, the aqueous solution of sodium silicate, lithium, and potassium is mentioned. As a thing containing aluminum sulfate, the powder quick-setting agent containing aluminum sulfate and the liquid quick-setting agent containing aluminum sulfate are mentioned.
The amount of the quick setting agent is not particularly limited, and can be used as described in the manufacturer's catalog, technical data, construction instructions, and the like.

The cement concrete of the present invention is not particularly limited as long as spraying is possible. As a general composition, for example, a slump of about 10 cm, W / C = about 60%, s / a = about 60%, a cement amount of about 360 kg / m ³ , and a gravel maximum dimension of 13 mm are often implemented. . In the high strength type, slump 20cm approximately, 25～35Cm in slump flow, W / C = 40~50% approximately, s / a = 60% approximately, the amount of cement 400~500kg / ^{m 3} approximately, with a maximum dimension 13mm gravel Often implemented.

  The aggregate used in the present invention is not particularly limited, and any commercially available aggregate may be used as long as it does not hinder spray construction.

  In the present invention, a water reducing agent, AE water reducing agent, high performance water reducing agent, high performance AE water reducing agent, cellulose ether, polyethylene oxide, polysaccharide thickener, etc. Various additives such as foaming agents, antirust agents, antifreeze agents, shrinkage reducing agents, polymer emulsions, setting accelerators, setting retarders, polymer flocculants, clay minerals such as bentonite and anion exchangers such as hydrotalcite Blast furnace granulated slag fine powder, blast furnace slow-cooled slag fine powder, admixtures such as fly ash and silica fume, and one or more of the group consisting of gypsums such as anhydrous gypsum can be used in combination. .

  The spraying method of the present invention is not particularly limited, but a wet spraying method in which a rapid setting agent is added to and sprayed with cement concrete that has been mixed by adding water that is pumped, and concrete in a dry state. The dry spraying method is applied in which the quick setting agent is pumped and the water is merged and sprayed before the nozzle.

"Experiment 1"
As the unit amount of each material are shown in Table cement 400 kg / ^{m 3,} fine aggregates 1058kg / ^{m 3,} coarse aggregate 710 kg / ^{m 3,} water 200 kg / ^{m 3,} the calcium carbonate (1) with respect to 100 parts of cement The amount was replaced with fine aggregate, and spray concrete was prepared as a high-performance water reducing agent 4 kg / m ³ . The sprayed concrete was pumped by a concrete pumping machine “MKW-25SMT” under conditions of a spraying pressure of 0.4 MPa and a spraying speed of 10 m ³ / h. Compressed air was introduced at a position 3 m behind from the Y-shaped pipe where the rapid setting agent was joined, and the concrete air was conveyed. The quick setting agent was pumped from one side of the Y-shaped pipe, mixed and mixed with cement concrete, and sprayed. About this quick setting shotcrete, the compressive strength, rebound rate, length change rate, and maximum temperature of the hardened body were measured. The results are shown in Tables 1 and 2.

(Materials used)
High-performance water reducing agent: polycarboxylic acid, commercially available coarse aggregate: Himekawa Sakegawa gravel, Itoigawa City, Niigata Prefecture, surface dry state, specific gravity 2.66, maximum dimension 13mm
Fine aggregate: Niigata Prefecture Itoigawa city Himekawa production river sand, surface dry state, specific gravity 2.62, maximum dimension 5mm
Cement: Ordinary Portland cement, commercially available calcium carbonate (1): Mined limestone crushed and particle size adjusted. Blaine specific surface area 1550 cm ² / g, purity 99.2%
Quick setting agent A: Calsim aluminate content, manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Natomic TYPE-5” (powder), addition rate: 7% with respect to 100 parts of cement
Quick setting agent B: Calsim aluminate contained, manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Natomic TYPE-10” (powder), addition rate: 10% with respect to 100 parts of cement
Quick setting agent C: Alkali metal silicate containing, commercial product, No. 3 water glass (liquid), addition rate: 8% as liquid with respect to 100 parts of cement
Quick setting agent D: Alkali metal aluminate content, manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Natomic TYPE-L” (liquid), addition rate: 8% as liquid with respect to 100 parts of cement
Quick setting agent E: Aluminum sulfate contained, manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Natomic LSA” (liquid), addition rate: 9% as liquid with respect to 100 parts of cement

(Measuring method)
Compressive strength: The compressive strength at the age of 24 hours is that the pin installed in the pullout formwork 25cm wide x 25cm long is covered with sprayed concrete from the surface of the pullout formwork, and the pin is pulled out from the back side of the formwork. The compressive strength was calculated from the formula of (compressive strength) = (pull-out strength) × 4 / (test specimen contact area). The compressive strength at the age of 28 days was determined by spraying rapidly setting sprayed concrete onto a formwork of width 50 cm x length 50 cm x thickness 20 cm. Measured and determined compressive strength.
Rebound rate: Shotcrete was sprayed on a simulated tunnel with a height of 3.5 m and a width of 2.5 m created in an arch shape with an iron plate for 10 minutes at a pumping speed of 10 m ³ / h. After that, (Rebound rate) = (Amount of quick setting sprayed concrete dropped without adhering to the simulated tunnel) / (Amount of quick setting shot concrete sprayed to the simulated tunnel) x 100 (%) did.
Length change rate: A specimen was prepared by spraying on a dedicated formwork (10 × 10 × 36 cm). After 1 day of age, the mold was removed and the base length was determined. After curing in a room at a temperature of 20 ° C. and a humidity of 60% for 28 days, the amount of shrinkage was measured. The measurement was based on JIS R 1129-3 (dial gauge method).
Maximum temperature increase rate: A temperature sensor was attached to the center of a mold having a width of 50 cm, a length of 50 cm, and a thickness of 20 cm, and sprayed concrete was sprayed. The maximum temperature of the sprayed concrete hardened body was measured with respect to the temperature of fresh concrete before spraying, and the ratio was defined as the maximum temperature increase rate. For comparison, the maximum temperature rise rate of the base concrete without the quick setting agent was also measured.
The measurement place was indoors, and the temperature change of the outside air during the measurement period was 16 ° C at the lowest and 22 ° C at the highest.

"Experimental example 2"
Based on the formulation of Experiment No. 1-15 in Experimental Example 1, the same procedure as in Experimental Example 1 was performed by changing the type of calcium carbonate. The results are shown in Table 3. For comparison, calcium carbonate Blaine specific surface area is more than 500 cm ² / g calcium carbonate below and 2000 cm ² / g was also evaluated.

(Materials used)
Calcium carbonate (2): Mined limestone crushed and particle size adjusted. Blaine specific surface area 450cm ² / g, purity 99.2%
Calcium carbonate (3): Mined limestone crushed and particle size adjusted. Blaine specific surface area 500 cm ² / g, purity 99.2%
Calcium carbonate (4): Mined limestone crushed and particle size adjusted. Blaine specific surface area 720 cm ² / g, purity 99.2%
Calcium carbonate (5): Mined limestone crushed and particle size adjusted. Blaine specific surface area 1050 cm ² / g, purity 99.2%
Calcium carbonate (6): Mined limestone crushed and particle size adjusted. Blaine specific surface area 1800cm ² / g, purity 99.2%
Calcium carbonate (7): Mined limestone crushed and particle size adjusted. Blaine specific surface area 2000 cm ² / g, purity 99.2%
Calcium carbonate (8): Mined limestone crushed and particle size adjusted. Blaine specific surface area 2150cm ² / g, purity 99.2%

  By using the spray material of the present invention, it becomes possible to suppress cracking by reducing the amount of shrinkage due to temperature stress and drying, and it is possible to obtain a shotcrete with excellent durability. For example, only shotcrete It is suitable as a spraying material for tunnel construction where lining work is performed.

Claims (2)

It contains calcium carbonate having a Blaine specific surface area of 500 to 1800 cm ² / g, a quick setting agent , cement, and an aggregate, the quick setting agent contains aluminum sulfate, and the calcium carbonate 2 with respect to 100 parts by mass of cement. The spray material which is -50 mass parts. Spraying method using a spray material according to claim 1 Symbol placement.